A. Field of the Invention
The invention relates to polyamide compositions having good flame retardant properties and improved moldability.
B. The Prior Art
The use of polyamide resins in molding compositions has become very widespread in recent years especially in end uses where toughness and high temperature stability are required properties. Speciality polyamide resins containing a variety of filler materials have been widely used in a range of automotive applications for example and other polyamides have been successfully introduced into the electrical, appliance and consumer goods fields.
Molding compositions usually require mold release agents. The first of such agents to be employed extensively was stearyl alcohol (disclosed in British Pat. No. 851,031). After it was determined that stearyl alcohol had a deleterious effect on flammability of the nylon the introduction of a fatty acid salt of aluminum, along with the alcohol, as taught in U.S. Pat. No. 3,988,271, was found to provide the same mold release characteristics along with good flame retardant characteristics.
Although the flame retardant-mold release resin system described in U.S. Pat. No. 3,988,271 was indeed an improvement over the prior art and satisfactory for many purposes, there were some disadvantages in its use. One such disadvantage was the formation of a gummy substance in molds, apparently the reaction product of the alcohol and the aluminum salt. Another disadvantage in the use of the resin system described in U.S. Pat. No. 3,988,271 was that aside from considerations attributable to the gummy residue, the melt flow of this resin system was insufficient for the most rapid operation of injection-type molding machines in the automatic mode.
It has now been discovered that with the use of the improved composition of this invention, the build-up of the gummy residue in the molding machines is substantially eliminated, with its resultant improvement in melt flow, all without sacrifice of good flame retardant characteristics.